1. Field of The Invention
The present invention relates to a plasma processing apparatus for processing vitreous workpieces therein, and in particular relates to a plasma processing apparatus having a plurality of processing chambers therein.
2. Description of Prior Art
An apparatus for use in plasma processing, having a plurality of processing chambers, has been proposed by the present inventors in Japanese Patent Application Laid-open No. Hei 9-306694 (1997), wherein ashing and/or etching treatments are conducted on a semiconductor wafer or a glass substrate for use in a liquid crystal display under a plasma atmosphere, thereby enabling processing of a large number of substrates in a short time.
The plasma processing apparatus disclosed in Japanese Patent Application Laid-open No. Hei 9-306694 (1997) uses a single high-frequency electric power source and distributes electric energy from this single high-frequency electric power source to each processing chamber through an electric power division means.
There is necessarily a difference between the two processing chambers in impedance. Furthermore, in a case of simultaneously discharging in the two processing chambers by using the single high-frequency electric power source, current is likely to flow into the side being lower in impedance, thereby causing a deviation or difference in etching rate or the like. Therefore, in Japanese Patent Application Laid-open No. Hei 9-306694 (1997) mentioned above, the electric power division means is constructed by a source-side copper plate, an electrode-side copper plate, and a copper bar for electrically connecting at arbitrary position between the copper plates, thereby allowing the impedances between the two processing chambers to be substantially equal to each other, including the electric power division means.
By using the electric power division means mentioned above, it is possible to obtain uniform processing to a certain extent. However, there are cases where it is impossible to make an adjustment or correction by means of the electric power division means mentioned above, depending upon the conditions of plasma generation such as gas flow rate, and pressure. For example, in the case where the gas flow rate is large and the pressure is high, a discharge is likely to being localized on one of the two chambers even if there is only a little difference in the impedance between them, and as a result, the difference in the processing speed or rate comes to be large.
For solving the aforementioned problems, the present invention provides an apparatus for plasma processing, having a plurality of processing chambers in which plasma is generated. A plasma processing apparatus according to the present invention comprises a plurality of first belt-like electrodes provided on the outer periphery of each processing chamber, and a plurality of second belt-like electrodes provided on the outer periphery of each processing chamber. Each first belt-like electrode and each second belt-like electrode is provided alternately and separated vertically with respect to each other. The first electrodes are commonly connected to a high-frequency electric power source, while the second electrodes are commonly connected to the earth, or to an electric power source which is lower in frequency than that of the high-frequency electric power source. Further, the first belt-like electrodes themselves are electrically connected to each other.
Electrical connection between the first belt-like electrodes is achieved by means of a belt-like conductor, having a width substantially equal to that of the first belt-like electrode, or else by a cable having low resistance and low impedance.
With the construction mentioned above, the plurality of the first electrodes disposed for the plurality of chambers can be considered as a single electrode, thereby enabling control of the difference in impedance for each processing chamber.